A Dark Spot on Your Palm or Sole — Why It's Different

Why a palm or sole spot is a different question

A pigmented spot on your palm, sole, or under a nail raises a different question than one on your forearm. These are the sites where acral melanoma tends to arise — a melanoma that begins on skin the sun rarely reaches. Ultraviolet light is the main modifiable driver of most skin cancers 1Ref 1National Cancer Institute (PDQ Screening and Prevention Editorial Board) (2025).Skin Cancer Prevention (PDQ®)–Health Professional Version.That ultraviolet radiation is the main modifiable risk factor for skin cancer, in contrast to the sun-protected acral sites where this melanoma arises., yet palms and soles get almost none of it, so the familiar reasoning about sun exposure offers no reassurance here.

That mismatch is the trap. A dark mark on skin that rarely sees daylight gets read as a bruise, a callus, or a stain — and the skin people are usually told to watch is sun-exposed skin, which is not where this melanoma lives. It can also show up as a band under a fingernail or toenail, where it is called subungual melanoma. The point is not that a dark palm spot is likely cancer; it is that the location removes the easy explanation you would reach for anywhere else.

What acral melanoma actually is

Acral melanoma is a melanoma of the acral skin — the palms, the soles, and the nail units. Like other melanomas, it is a cancer of melanocytes, the cells that produce pigment, and when it is caught early it is removed surgically, sometimes with sampling of a nearby lymph node, or treated with immunotherapy or targeted drugs when it has spread 2Ref 2National Cancer Institute (PDQ Adult Treatment Editorial Board) (2025).Melanoma Treatment (PDQ®)–Health Professional Version.That melanoma is a cancer of melanocytes treated with surgical excision, sometimes lymph-node sampling, and immunotherapy or targeted therapy in advanced disease.. Its full clinical name is acral lentiginous melanoma.

What makes it distinct is not how it is treated but where it grows and how it is missed. Because it can be painless and slow at first, and because a sole or a palm is rarely part of anyone's self-check, it is often found later than melanomas on the trunk or face. Some acral melanomas carry little or no pigment at all — an amelanotic melanoma — which makes a firm pink or red patch just as worth checking as a black one. Melanoma is less common in darker skin, but the old belief that darker skin does not get skin cancer is dangerous: acral melanoma spares no one, and skin cancer in skin of color is too often caught late.

The features that should raise your concern

No single feature proves a spot is or isn't melanoma, but a short checklist tells you when to stop watching and get it seen. Dermatologists teach the ABCDE signs: asymmetry, an irregular or blurred border, more than one color, a diameter larger than a pencil eraser, and — most important — evolution, meaning any change in size, shape, or color over weeks or months 3Ref 3Abbasi NR, Shaw HM, Rigel DS, et al. (2004).Early diagnosis of cutaneous melanoma: revisiting the ABCD criteria.The ABCDE features — asymmetry, border irregularity, color variation, diameter over 6 mm, and evolution — used to flag a pigmented lesion for evaluation.. On a palm or sole, two acral-specific cues matter alongside those.

• A pigment band under a nail that is widening, especially one spreading onto the surrounding skin or the nail fold, is a classic warning sign.
• A spot with an irregular, blurred edge, or one that keeps enlarging, on the weight-bearing skin of the sole.

The honest limit is simple. These are the criteria for acting, not a way to rule melanoma out. A spot that fails every one of them can still deserve a look if it is new or unexplained, and no checklist substitutes for a trained eye on the actual lesion. That is why the criteria tell you when to go — not whether you are safe to stay home.

What else it could be — and why that doesn't settle it

Plenty of harmless things darken a palm or sole, and most dark spots there are not cancer. A blood blister from friction or sport — sometimes called a black heel or talon noir — can look alarming and is harmless. So can a splinter, ground-in dirt lodged in a deep crease, a wart speckled with tiny dark dots, or an ordinary mole you have had for years. The catch is that none of these can be told apart from melanoma by eye alone.

That is exactly why this page will not tell you your spot is fine. The clues that point toward a benign cause are in the story, not the appearance: a friction blister usually follows a bout of activity and fades over a week or two, dirt rubs off, a splinter has a history. A pigmented spot with no clear cause, one that stays put and slowly grows, or one you simply cannot explain is the one that earns a professional look. When the story does not fit a benign cause, the criteria decide the next step, not hope.

How a dark spot is actually evaluated

A clinician looks at the spot in person, often with a dermoscope — a handheld lens that reveals pigment patterns the naked eye misses — and decides whether it can be watched or needs sampling. If melanoma is a genuine possibility, the standard is a biopsy that removes the whole lesion or takes a narrow full-thickness sample rather than a shallow shave, so the pathologist can measure how deeply it reaches 4Ref 4Swetter SM, Tsao H, Bichakjian CK, et al. (2019).Guidelines of care for the management of primary cutaneous melanoma.That for a suspected melanoma an excisional or narrow full-thickness biopsy is preferred over a superficial shave so tumor depth can be measured.. That depth measurement drives everything that follows.

You do not always have to start with an in-person visit. A dermatologist can review clear, well-lit photographs through a teledermatology service and advise how urgently to be seen 5Ref 5American Academy of Dermatology (2024).Teledermatology Standards.That teledermatology lets a dermatologist review photographs of a lesion, with published standards for image quality and handling.; the American Academy of Dermatology publishes standards for how those images should be captured and handled. Either way, the most useful thing you can do today is photograph the spot beside a ruler or coin for scale and note the date, so any change can be measured rather than remembered.

How fast to be seen, and why early matters

Weeks, not months. A spot that is stable and long-standing is lower priority than one that is new, growing, changing color, bleeding, or spreading toward a nail — and anything changing quickly should move up the calendar. Urgency helps because melanoma is far more treatable early: while it is still confined to the skin, five-year relative survival is around 99 percent, but once it has spread to distant sites that figure falls to roughly a third 6Ref 6National Cancer Institute, Surveillance, Epidemiology, and End Results (SEER) Program (2025).Cancer Stat Facts: Melanoma of the Skin.US five-year relative survival for melanoma: about 99 percent when localized to the skin, falling to roughly one-third once it has spread to distant sites..

That gap is the whole argument for not waiting. A melanoma on the foot found as a thin, early lesion carries a very different outlook than the same cancer found late — which is why a black spot on the sole of the foot is worth a look rather than a wait-and-see. Photograph the spot, track whether it is changing, and have it examined in weeks rather than months.